This invention relates to abrasive discs for use with orbital sanders which are designed for use with integral vacuum exhaust systems. Orbital sanders generate a great deal of dust, particularly when used on wood, polymer composites or unmodified plastics or painted surfaces. This dust is not only inconvenient and possibly injurious to health, but it also obscures the view of the surface being sanded and can “blind” the abrasive disc being used. Many manufacturers therefore sell orbital sanders with integral or readily attachable vacuum exhaust systems design to suck away the dust as it is formed. This is done by applying a vacuum to the back of the support pad to which the abrasive disc is attached and providing holes through the support pad and the disc through which the dust can be evacuated as it is generated.
However there is a problem in that the pattern of exhaust holes in the backup pads is not standardized such that abrasive discs intended for use with, for example a Black & Decker Corporation orbital sander, will not fit a sander sold by Porter-Cable Corporation. One type has five exhaust holes whereas the other has eight exhaust holes. Yet another sander, the Dynabrad, has six holes. This means that the retailer selling to the “Do It Yourself” (or DIY) market must keep at least three different stocks of abrasive discs, in all grit sizes, if he is to be able to service the needs of all his customers. This consumes valuable shelf space which becomes very inconvenient as the number of DIY products for which replacement abrasive materials must be stocked increases.
One solution to this problem is proposed in U.S. Pat. No. 5,810,650 which describes an abrasive disc with a multitude of spaced perforations all across the disc surface. The disc is backed by a porous material and swarf generated during grinding is sucked through the porous backing and ejected at the sides or, if a grinder with a vacuum extractor system is fitted, through the exhaust ports. This does however sacrifice a good deal of effective grinding surface and requires a backing with sufficient porosity to allow passage of the swarf without becoming prematurely clogged.
Another option is described in U.S. Pat. No. 5,989,112 which describes a disc for use with vacuum sanders with the five hole or eight hole pattern of exhaust ports in the backing pad. In this disc there are eight holes, as appropriate for the eight hole vacuum sander but selected holes are enlarged to coincide also with the location of the holes in a five hole orbital sander device. This works very well but the disc needs to be located on the backup pad with care to make sure the holes are in register with the holes in the backup pad. It is found however, that many workers value more highly the ability to make a disc change without even looking at the disc orientation on the backup pad. There is therefore the need for an abrasive disc for attachment to a backup pad fitted with exhaust ports that can be fitted quickly and that will not be sensitive to orientation with respect to the backup pad and will still be effective to remove swarf from the grinding surface.